Zinc sulfide and zinc selenide are used in applications requiring long wavelength infrared transmission capability such as missile domes. Zinc sulfide is a principal window material for air borne FLIR systems. These compounds are some of the most chemically and mechanically durable materials which are transparent in the infrared range of the electromagnetic spectrum to approximately 10 micrometers, are available in useful sizes, and have potential for transmission in the visible range of the spectrum. A problem with these compounds is that they do not have adequate transmission in the visible and near-infrared range of the electromagnetic spectrum. Additional applications for these compounds could be developed if their transparency at visible and near-infrared wavelengths could be improved. More specifically, they could then be used in applications requiring multi-spectral capability. While their far-infrared wavelength limitation is an intrinsic property of the material and is related to multi-phonon absorption, their short wavelength limitation is determined by several incompletely characterized extrinsic effects.